Generally, lighter-than-air vehicles, hereinafter airships, utilize photovoltaic arrays, also referred to as solar arrays, for the generation of power. This power is utilized to control operation of propulsion systems, communications equipment, and also surveillance instruments that may be carried by the airship.
Photovoltaic, or solar, arrays comprise a plurality of cells that are fundamentally designed to have high absorptivity in the solar visible and near visible infrared light spectrums. A fraction of this absorbed spectral energy is converted to electromotive power, also referred to as electrical energy, which is the inherent function of a solar or photovoltaic cell. Much of the remainder of the absorbed solar spectrum is converted to heat, thereby increasing the temperature of the cell and, via conduction, any underlying structures. Skilled artisans will appreciate that this extra heat can have detrimental effects on the underlying structures.
In certain applications of the photovoltaic array, such as in space and near-space regenerative power systems and for building roof or curtain-wall solar arrays, there may be times of the day or year when the benefits of photovoltaic electric generation are out weighed by the deleterious effects of sub-structural heating. For example, in a high-altitude airship, when the solar arrays are adequately powered and all energy storage capacity is utilized, absorption of extra heat in the airship may cause the supporting structure to over-heat and adversely effect the control and positioning of the airship. It is also conceivable that the extra absorbed heat could adversely effect any communications or optical equipment carried by the airship. Therefore, there is a need in the art to provide a way to reduce the impact of the excessive heat by controlling the amount of solar radiation that is exposed through the photovoltaic array when part or all of the solar array are not needed for electrical energy generation. 